1. Field of the Invention
This invention relates to an insulator for a multi-power system, which is used to resolve the current leakage that comes from the power supplied to the corresponding devices which are not being operated.
2. Description of the Related Art
In a personal computer system, a common device is the power management unit. The system can have different power consumption with differently operating modes by using the power management unit. The differently operating modes, referring to FIG. 1, includes an operating power mode (referred to as a VCC mode hereinafter) for a circuit 11, such as a main circuit, a standby power mode (referred to as a VSB mode hereinafter), and a battery mode (referred to as a VBAT mode hereinafter). A standby power or a battery is applied when the system is not operated. In other words, the system enters into a VSB mode or a VBAT mode based on the selection of a selector 12. The selected mode is referred to as a real-time voltage (VRTC) mode to power a circuit 13, such as a power control circuit. At this point, if the power consumption on a standard power or a battery is minimized, we can effectively increase the system power utilization without the influence on a normal operation with the operating power in the system. However, when a PC is connected with its peripheral devices, a voltage leakage occurs from the peripherals to the VCC power supply on the PC board if the power applied to the peripherals is not reduced after the power is supplied to the PC. The voltage leakage is about 0-1.5V. Even though the value of the voltage leakage is small, the value will cause different input signal levels between the power VCC and the power VSB or VBAT. That is, the standby circuit powered by the power VSB or VBAT may receive an unknown voltage state, so as to make a correct response impossible. Therefore, a current leakage happens in this situation.
Referring to FIG. 2, a shifter is shown in U.S. Pat. No. 5,223,751. In FIG. 2, Vc and Vr are two power supply levels with about 3V and about 5V respectively, PIN is an input signal and POUT is an output signal. As shown in FIG. 2, when Vc=IN is higher than the NMOS threshold voltage but insufficient to turn the voltage level of the node B from logic high to logic low, such a shifter may have current leakage. When Vc=0V, the node B is floated. At this point, block 26 may have current leakage if the immediately previous input state of block 26 is on logic low.
Both examples as mentioned above cause the current leakage so as to waste the power resources of the system. To reduce the power consumption when not operating, a shifter or an isolating device, such as insulator, is needed for a multi-power system to reduce the current leakage, thereby increasing the efficiency of the power utilization.
Therefore, an object of the invention is to provide an isolating device, which can avoid the current leakage when power is switched to different levels, thereby effectively utilizing power resources.
To realize the above and other objects, the invention provides an isolating device. The isolating device includes: a first power supply for providing an operating power to the isolating device; a level detector for detecting the voltage level of the operating power; a signal isolation controller for changing the output level of the circuit supplied by the operating power based on the operating power detected; and a second power for supplying a real-time power to circuit for power saving operation based on the changed output level.
Accordingly, when the isolating device of the invention is provided to completely or mostly reduce the current leakage, a system with multi-power can prevent the current leakage when power is switched to different levels, so that the system can not only save the power consumption but also avoid an operating mistake in the system.